gistfile1.cs

namespace GitHub.Tests.Helpers
{
    public class ZeroMqRxFixture
    {
        [Test]
        public void ClientServerSmokeTest()
        {
            string socketAddr = "tcp://localhost:19999";

            var server = ZeroMQHost<string>.Create(() =>
            {
                var socket1 = new Socket(SocketType.REP);
                socket1.Bind(socketAddr);
                return new[] {socket1};
            });

            server.SubscribeToSocket(socketAddr)
                .Subscribe(x => x.Response.OnNext("***" + x.Value));

            var client = ZeroMQHost<string>.Create(() =>
            {
                var socket2 = new Socket(SocketType.REQ);
                socket2.Connect(socketAddr);
                return new[] {socket2};
            });

            string result = null;

            IObserver<string> sender = client.SenderForSocket(socketAddr);
            client.SubscribeToSocket(socketAddr)
                .Subscribe(x => result = x.Value);

            sender.OnNext("Hello");

            int retries = 10;
            while(retries-- > 10 && result == null)
            {
                Thread.Sleep(1000);
            }

            Assert.AreEqual("***Hello", result);
        }
    }
}

Just make sure you dispose of the ManualResetEvent, they leak handles.